This invention relates to a drive system for a and in particular to a system in which a vehicle may be propelled either by an electric motor or by an internal combustion engine.
In such a system it is commonly required to change from electrical to internal combustion power while the vehicle is running, and in known systems it has been the practice to match the engine and motor speeds by operating the engine throttle. However before the engine shaft is engaged with an output shaft of the system the response of the unloaded engine to throttle adjustments results in the engine speed hunting above and below its desired value. The consequent mismatch of the engine and motor speeds is likely to result in damage or severe wear to a clutch used to couple the engine to the output shaft.